A conventional tandem drive axle system for commercial vehicles includes front and rear axle assemblies and an intermediate drive shaft assembly connecting the two axle assemblies. The front and rear axle assemblies each include a pair of axle half shafts extending therefrom on which one or more wheels of a vehicle are mounted. The axle half shafts in each axle assembly are driven by a wheel differential.
Tandem drive axle systems can employ an inter-axle differential to divide power between the front and rear axle assemblies. The inter-axle differential enables speed differences between the drive axles to balance the torque between the drive axles during the vehicle cornering, to compensate for tire size differences, etc.
Components of the tandem drive axle system may be selected based on a gear reduction ratio present in an axle. Axle ratios may be of a two-speed configuration to permit the vehicle to operate in a low speed and high torque manner or in a high speed and low torque manner. It is preferred to drive both axles when the low speed and high torque manner of operation is desired and it is advantageous to operate only a single axle of the tandem drive axle system when the high speed and low torque manner of operation is desired.
Additionally, an axle can be disengaged from the drive axle system when the tractive effort of all axles is not required. Disengaging the axle can result in reduced spin loses during highway cruise conditions. However, the engaged axle can experience increased torque and cycles leading to increased accumulated damage and reduced durability.
When the torque is increased on an axle, the transfer of torque between two relatively moving and engaged components of the driveline can cause damage to gear teeth and bearings of the driveline, reducing the durability and lifespan of the axle system.
Therefore, it would be advantageous to prevent damage to the axle system by limiting the damage to the driveline caused by excessive torque and speed.